Distribution of Organic Carbon in Surface Sediments of the Continental Shelf off the Indus Delta of Pakistan

Abstract

Surface sediments collected from the continental shelf off the Indus delta, Pakistan, were studied to determine the organic carbon content. The results suggest that textural characteristics influence the distribution of the organic carbon content in the sediments of the Indus shelf. The surface sediments of the Indus shelf are predominantly silt, silty clay and clayey silty sand. Generally, inner shelf sediments contain 50-70% silt and ~20% clay. A belt of coarser sediments containing >50% sand occurs in the North West outer shelf region. The fine clay content in the sediments increases with depth, from 20% at the Indus river mouth to 60% at the continental slope region. Sediments of the Indus shelf contain

a relatively high (~1.0%) content of organic carbon, and their distribution indicates textural influence. The coarse, silty sediments (50-70% silt) have a low organic carbon content of <1.0%. The fine-grained clayey sediments (20-40% clay) are characterized by relatively high (1-2%)

organic carbon content. The highest organic carbon content of 2-3% occurs in fine-grained sediments of the outer shelf and the continental slope area, where 60% of the sediments are clayey sediments.

Keywords

• Organic Carbon,Surface Sediments,Texture,Indus Continental Shelf

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